Exploring the Synthetic Potential of γ-Lactam Derivatives Obtained from a Multicomponent Reaction-Applications as Antiproliferative Agents.

A study on the reactivity of 3-amino α,ß-unsaturated γ-lactam derivatives obtained from a multicomponent reaction is presented. Key features of the substrates are the presence of an endocyclic α,ß-unsaturated amide moiety and an enamine functionality. Following different synthetic protocols, the functionalization at three different positions of the lactam core is achieved. In the presence of a soft base, under thermodynamic conditions, the functionalization at C-4 takes place where the substrates behave as enamines, while the use of a strong base, under kinetic conditions, leads to the formation of C-5-functionalized γ-lactams, in the presence of ethyl glyoxalate, through a highly diastereoselective vinylogous aldol reaction. Moreover, the nucleophilic addition of organometallic species allows the functionalization at C-3, through the imine tautomer, affording γ-lactams bearing tetrasubstituted stereocenters, where the substrates act as imine electrophiles. Taking into account the advantage of the presence of a chiral stereocenter in C-5 substituted γ-lactams, further diastereoselective transformations are also explored, leading to novel bicyclic substrates holding a fused γ and δ-lactam skeleton. Remarkably, an example of a highly stereoselective formal [3+3] cycloaddition reaction of chiral γ-lactam substrates is reported for the synthesis of 1,4-dihidropyridines, where a non-covalent attractive interaction of a carbonyl group with an electron-deficient arene seems to drive the stereoselectivity of the reaction to the exclusive formation of the cis isomer. In order to unambiguously determine the substitution pattern resulting from the diverse reactions, an extensive characterization of the substrates is detailed through 2D NMR and/or X-ray experiments. Likewise, applications of the substrates as antiproliferative agents against lung and ovarian cancer cells are also described.

Multicomponent Synthesis of Unsaturated γ-Lactam Derivatives. Applications as Antiproliferative Agents through the Bioisosterism Approach: Carbonyl vs. Phosphoryl Group.

We report efficient synthetic methodologies for the preparation of 3-amino and 3-hydroxy 3-pyrrolin-2-ones (unsaturated γ-lactams) through a multicomponent reaction of amines, aldehydes and acetylene or pyruvate derivatives. The densely substituted γ-lactam substrates show in vitro cytotoxicity, inhibiting the growth of the carcinoma human tumor cell lines RKO (human colon epithelial carcinoma), SKOV3 (human ovarian carcinoma) and A549 (carcinomic human alveolar basal epithelial cell). In view of the possibilities for the diversity of the substituents that offer a multicomponent, synthetic methodology, an extensive structure-activity profile is presented. In addition, the bioisosteric replacement of the flat ester group by a tetrahedral phosphonate or phosphine oxide moiety in γ-lactam substrates leads to increased growth inhibition activity. Cell morphology analysis and flow cytometry assays indicate that the main pathway by which our compounds induce cytotoxicity is based on the activation of the intracellular apoptotic mechanism.

A Multicomponent Protocol for the Synthesis of Highly Functionalized γ-Lactam Derivatives and Their Applications as Antiproliferative Agents.

An efficient synthetic methodology for the preparation of 3-amino 1,5-dihydro-2H-pyrrol-2-ones through a multicomponent reaction of amines, aldehydes, and pyruvate derivatives is reported. In addition, the densely substituted lactam substrates show in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines HEK293 (human embryonic kidney), MCF7 (human breast adenocarcinoma), HTB81 (human prostate carcinoma), HeLa (human epithelioid cervix carcinoma), RKO (human colon epithelial carcinoma), SKOV3 (human ovarian carcinoma), and A549 (carcinomic human alveolar basal epithelial cell). Given the possibilities in the diversity of the substituents that offer the multicomponent synthetic methodology, an extensive structure-activity profile is presented. In addition, both enantiomers of phosphonate-derived γ-lactam have been synthesized and isolated and a study of the cytotoxic activity of the racemic substrate vs. its two enantiomers is also presented. Cell morphology analysis and flow cytometry assays indicate that the main pathway by which our compounds induce cytotoxicity is based on the activation of the intracellular apoptotic mechanism.

Asymmetric Synthesis of Tetrasubstituted α-Aminophosphonic Acid Derivatives.

Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the past few decades. In the following lines, the existing literatures for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.

Ugi Reaction on α-Phosphorated Ketimines for the Synthesis of Tetrasubstituted α-Aminophosphonates and Their Applications as Antiproliferative Agents.

An Ugi three-component reaction using preformed α-phosphorated N-tosyl ketimines with different isocyanides in the presence of a carboxylic acid affords tetrasubstituted α-aminophosphonates. Due to the high steric hindrance, the expected acylated amines undergo a spontaneous elimination of the acyl group. The reaction is applicable to α-aryl ketimines bearing a number of substituents and several isocyanides. In addition, the densely substituted α-aminophosphonate substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell line A549 (carcinomic human alveolar basal epithelial cell).

Brönsted Acid Catalyzed Multicomponent Synthesis of Phosphorus and Fluorine-Derived γ-Lactam Derivatives.

A Brönsted acid multicomponent reaction between pyruvate derivatives, amines, and aldehydes for the preparation of phosphorus and fluorine substituted γ-lactam derivatives is presented. Depending on the substitution in the resulting 1,5-dihydro-2H-pyrrol-2-one substrates, the reaction provides enol- or enamine-derived γ-lactams. Some enantioselective examples of this reaction are also reported using chiral phosphoric acids as organocatalysts. Moreover, several synthetic applications of γ-lactam derivatives are presented including some examples of highly diastereoselective transformations.

Enantioselective Aza-Reformatsky Reaction with Ketimines.

Here, an enantioselective aza-Reformatsky reaction using acyclic ketimine substrates is presented. Using α-phosphorated ketimines as electrophilic substrates and a simple BINOL-derived ligand, phosphorated analogues of aspartic acid holding chiral tetrasubstituted carbons are efficiently obtained with excellent enantioselectivity through an asymmetric organocatalytic Reformatsky-type reaction. The phosphorated analogues of aspartic acid have been used for the synthesis of phosphorus-containing enantiopure tetrasubstituted ß-lactams.

Enantioselective α-Aminophosphonate Functionalization of Indole Ring through an Organocatalyzed Friedel-Crafts Reaction.

Chiral phosphoric acids efficiently catalyze the asymmetric Friedel-Crafts reaction of several indoles with α-iminophosphonates to afford enantioenriched hybrid α-aminophosphonate functionalized indole derivatives.

Synthesis of novel antiproliferative hybrid bis-(3-indolyl)methane phosphonate derivatives.

An efficient synthetic methodology for the preparation of phosphorus substituted bis-(3-indolyl)methane through a double nucleophilic addition of indole derivatives to an in situ generated α-iminophosphonate is reported. In addition, bis-(3-indolyl)methane substrates showed in vitro cytotoxicity, inhibiting the growth of carcinoma human tumor cell lines A549 (carcinomic human alveolar basal epithelial cell) and SKOV03 (human ovarian carcinoma).

Brönsted-Acid-Catalyzed Asymmetric Three-Component Reaction of Amines, Aldehydes, and Pyruvate Derivatives. Enantioselective Synthesis of Highly Functionalized γ-Lactam Derivatives.

Chiral phosphoric acids are efficient organocatalysts for the asymmetric three-component reaction of amines, aldehydes, and pyruvate derivatives. Simultaneous condensation of amines with both carbonylic compounds followed by a hydrogen bonding activated nucleophilic addition of enamines to imines affords densely functionalized enantioenriched 1,5-dihydro-2H-pyrrol-2-ones. These substrates can be used in subsequent diastereoselective transformations to afford enantiopure γ-lactam derivatives.